REUTERS - Top generals, ambassadors and some tribes threw their support behind Yemen's anti-government protesters on Monday in a major blow to President Ali Abdullah Saleh as he tries to survive growing demands for his immediate departure.

The president, a perennial survivor who has stayed in power for 32 years throughout a civil war, numerous uprisings and militant campaigns, has seen a string of allies break ranks with him in recent days.

Despite that, pan-Arab TV channel Al Arabiya quoted Saleh as saying the majority of Yemenis were with him and that he was "holding on", while Al Jazeera said he had asked Saudi Foreign Minister Saud al-Faisal to mediate in the worsening crisis.

Defence Minister Mohammad Nasser Ali said on Monday that the army still backed Saleh.

"The armed forces will stay faithful to the oath they gave before God, the nation and political leadership under the brother president Ali Abdullah Saleh...," Ali said in a statement read out on state TV.

"We will not allow under any circumstances an attempt at a coup against democracy and constitutional legitimacy, or violation of the security of the nation and citizens."

Yemeni television showed footage of Saleh, facing popular protests against his 32-year rule, swearing in new members of the appointed Shura Council, Yemen's upper house of parliament.

The latest defections and resignations were apparently sparked by Saleh's decision to resort to violence to deal with the continuing protests against his rule.

On Friday snipers killed 52 anti-government protesters in Sanaa, prompting Saleh to sack his cabinet and declare a state of emergency for 30 days that restricts freedom of movement and the right to gather and gives police more power of arrest. On Monday mourners buried some of the dead.

But the televised announcement of defection by powerful General Ali Mohsen on Monday was a major setback to Saleh.

"We announce our peaceful support for the peaceful revolution of the youth and their demands and we carry out our duty ... in ensuring security and stability in the capital," Mohsen, commander of the northwest military zone, said on Al Jazeera television.

"Yemen today faces a serious crisis ... as a result of unconstitutional and illegal practices by the authorities, a policy of marginalisation and absence of justice," Mohsen said.

"Repressing peaceful demonstrators in public areas around the country has led to a cycle of crises which is getting more complicated each day and pushing the country toward civil war."

Mohsen is a kinsman of Saleh from the influential al-Ahmar tribe, whose members hold many key positions in the state.

The al-Ahmar is a tribal group in the Hashed federation, a key pillar of Saleh's rule which has relied on balancing tribal forces -- in detriment to state-building and national unity, critics say.

But al-Ahmar support for Saleh appears to be crumbling, with their tribal chief Sheikh Sadeq al-Ahmar expressing support on Al Arabiya for the protest movement.

Arabic satellite channels said two other generals announced their support for the protesters, including another al-Ahmar - Mohammed Ali Mohsen al-Ahmar, commander of the eastern military section, and Hamid al-Qosheibi, commander of the Amran region.

No clear successor

Saleh has no clear successor, one reason why his closest allies Washington and Saudi Arabia -- have sometimes appeared nervous about his stepping aside in the face of the uprising.On Monday French Foreign Minister Alain Juppe began the first Western official to say Saleh should stand down.

Western countries are concerned over the unrest in Yemen given the absence of a clear alternative leader and because of Saleh's help in fighting al Qaeda, which has tried to mount attacks against the United States and neighbouring Saudi Arabia.

The United States, which along with Yemen's main financial backer Saudi Arabia, has long seen Saleh as a bulwark against a dynamic al Qaeda network in the Arabian Peninsula, has called for dialogue on a "peaceful transition".

On Monday, Yemen's ambassadors to Syria, Saudi Arabia, Lebanon, Egypt, the Arab League and China were among senior diplomats resigning or expressing support for the protest movement, as well as Abdullah Alaiwa, a former defence minister and adviser to the army staff, Al Jazeera said.

"I am resigning after the massacre that happened at the Taghyir (Change) Square," Abdel-Wahhab Tawaf told Al Jazeera from the Syrian capital Damascus.

The governor and his deputy in Aden, a port city at the centre of the secessionist movement, and the deputy speaker of parliament and several ruling party MPs were among others who expressed support for the protest movement.

Yemen has been in ferment since popular revolts in Egypt and Tunisia removed entrenched rulers Zine al-Abidine Ben Ali and Hosni Mubarak in January and February.

From an early stage Saleh made verbal concessions, such as promising to quit in 2013 without bequeathing power to his son and, last week, offering a new constitution giving more powers to parliament, as well as announcing an array of handouts.

But he rejected opposition plans for a phased transition of power this year, even as he haemorrhaged support from previously allied tribes, Islamist clerics and politicians.

His government has failed to meet the basic needs of Yemen's 23 million people. Unemployment is around 35 percent -- rising to 50 percent for those aged between 18 and 28, according to U.N. figures. Oil wealth is dwindling. Water is running out and more than two-fifths of Yemenis live in poverty.